The gap between Cunliffe and Key in the polls may be turning into a chasm, but the Labour grassroots won’t be ready to throw in the towel yet. Belief in the last minute game-changer is what keeps the foot soldiers going.

And MMP helps keeps the dream alive too – it makes the mountain a little smaller.

If you are a National supporter, the hero’s welcome for Key will be heartfelt. He has led National to a place those attending this weekend’s conference could barely imagine just a decade ago.

That was when Don Brash took over a dispirited and demoralised National caucus from Bill English. Brash was their last roll of the dice to avoid oblivion in 2005.

It worked – to a point. But it took Key to make National look like winners again.

Cunliffe has not yet managed to invest his leadership with the same transformative power.

Voters struggle to imagine him as the next prime minister. Consequently, the party’s policy announcements are not getting much traction. To resonate, voters must believe Labour can make it happen, and on present polling – 30 per cent and sinking – that is a big ask.

It’s Catch-22.

Some of Cunliffe’s colleagues would blame him for that result. They never wanted Cunliffe as leader and the polls are vindication, while many of the grassroots would blame Cunliffe’s caucus and the knives are already out for some.

Others blame the media, or jump at shadows and conspiracy theories.

The fact that so many National MPs seemed to know about the Donghua Liu allegations that dragged Cunliffe through the mud feeds their theory that the story was National’s ‘‘H-bomb’’ - so-called in honour of Labour’s attempted H-bomb smear targeting Key in 2008.

That theory is mostly fanciful.

National could not have planned for Cunliffe’s stumble over his brush with the wealthy Chinese donor 11 years ago.

But it is true that National has ruthlessly exploited any stumble. Put simply, National seems hungrier to win than Labour.

That may not be surprising – power is addictive and National MPs will fight tooth and nail to keep it.

And National has one weapon up its sleeve that Labour does not, which it will use to its advantage: the power of incumbency.

Key’s trip to Washington could not have painted a starker picture of where the two leaders were at. Key got to rise above domestic quibbles, while Cunliffe was back home trying to pull himself out of quicksand.

The danger for Labour is that a siege mentality has taken root. Some of those close to Cunliffe are clearly at their wits end. Conversations with journalists have ended in shouting.

It caused barely a ripple this week when two Labour MPs, Damien O’Connor (West Coast Tasman) and Rino Tirikatene (Te Tai Tonga), crossed the floor to vote with the Government on legislation to allow the logging of wind-fall native trees.

O’Connor has always been given a long rope by Labour when it comes to West Coast issues of course, but it is an indication that Labour MPs are in a quiet panic about their futures and more intent on protecting their seats than bolstering the party vote.

National is stirring things up as well by unsettling the likes of long-time Labour strategist Trevor Mallard in his Hutt South seat, which Key has been visiting frequently in support of the National candidate Chris Bishop.

The launch of Labour’s shadow Budget was supposed to mark a turning point when Labour regained its footing. Instead it was overshadowed by Cunliffe’s apparent threat to sue some media over their Liu coverage.

Incumbency trumps Labour again in the battle of the party conferences.

Key’s speech will lay out his agenda for a third term. From where National sits in the polls, it’s hard for voters not to invest it with greater authority.

Key says the speech on Sunday will brush over the issue of tax cuts; he insists no decision has yet been made – in other words he is keeping his powder dry for a big bang announcement on the campaign trail. National knows the ‘‘battlers’’ in the low to middle income bracket are looking for a dividend from the economic recovery and tax cuts are the obvious way to deliver that, modest though they will be.

If there was a hole in Labour’s alternative Budget this week, that was it.

It took from the rich, by hiking taxes on income of more than $150,000, but it deferred the day when payback would be delivered to the not-so-rich through tax cuts, which won’t happen until a second term.

But National’s attack on the shadow Budget was muted. There was the obligatory lash about raising taxes but then National can hardly complain too loudly given it has also raised taxes by hiking GST, even if it argues the impost was neutral.

The lacklustre response can suggest only one of two things: Labour did its homework on the shadow Budget and left National no room for easy attack lines. Or National doesn’t believe the policy debate is where the election will be won.